README_NAAMES_CDOM

Updated 7/21/16 nbn

These CDOM spectra were measured from samples collected and prepared according to the 
UCSB CDOM Laboratory protocol (Nelson et al., 2007). Samples were analyzed in an UltraPath 
spectrophotometer according to the same method with recent modifications as specified by 
the draft NASA CDOM Group UltraPath analysis protocol (reference TBA). 

Samples are collected from Niskin bottles using silicone tubes by analysts wearing nitrile gloves. 
The samples are collected into combusted 60ml brown borosilicate glass EPA vials with Teflon 
lid liners. 

To remove particles the samples are filtered through 0.2 micron pore 25mm Nuclepore 
polycarbonate filters that have been pre-extracted with 60ml ultrapure water (Barnstead 
Nanopure, 18M? cm, low carbon filter cartridge). 

Samples are stored at 4C in the dark until analysis, generally within 6 months to 1 year. 2-year 
stability of samples stored in this manner has been documented by Swan et al. (2009). 

On analysis day sample vials are allowed to equilibrate to room temperature and are analyzed 
for UV and visible absorbance in an UltraPath single-beam long path (200cm cell) 
spectrophotometer. Samples are referenced against ultrapure water (Barnstead Nanopure, 
18M? cm, low carbon filter cartridge) and are corrected for refractive index effects using 
concurrently measured apparent absorption spectra of 30 g/l and 40 g/l solutions of sodium 
chloride (SigmaUltra > 99.97% NaCl), interpolated by the salinity of the sample. Corrected 
spectra are converted to naperian absorption coefficient by the formula a = 2.303A/l where A is 
the decadal absorbance of the sample, l is the pathlength (m), and 2.303 converts decadal to 
natural log scale. 

Reference spectra of a water solution of Suwanee River Fulvic Acid Standard 1, IHSS #1S101F 
(http://www.humicsubstances.org/elements.html) vs ultrapure water at approximately 0.25 
mg/l is also measured at the time of sample analysis, and is converted to specific absorption 
(m2/mg). 

All spectra are null corrected at long wavelength (690-710 nm avg), in accordance with the 
current draft protocol. 

Reported data include the CDOM spectrum (ag), the estimated error (based on the average of 
~6 scans over 30 s, propagated through the analysis arithmetic), the raw absorbance average 
and its standard deviation, and the SRFA and NaCl reference spectra. 

References:

Nelson, N.B., D.A. Siegel, C.A. Carlson, C. Swan, W.M. Smethie, Jr., and S. Khatiwala, (2007). 
Hydrography of chromophoric dissolved organic matter in the North Atlantic. Deep-Sea Res. 
54, 710-731.
Swan, C.M., D.A. Siegel, N.B. Nelson, C.A. Carlson, and E. Nasir (2009) Biogeochemical and 
hydrographic controls on chromophoric dissolved organic matter distribution in the Pacific 
Ocean. Deep-Sea Res. I 56: 2175-2192.